1. Field of the Invention
The invention relates to forging manipulators of the kind comprising a gripper support and a manipulator truck, the gripper support being pivotably supported by means of a front and a rear linkage on the frame of the manipulator truck, which advantageously reciprocates continuously in the direction of a forging press, and being controllably axially movable in the forward and reverse direction in relation to the manipulator truck from a middle position by hydraulic piston-cylinder units pivotably mounted on the one hand on the frame of the manipulator truck and on the other hand on the gripper support.
2. Description of the Prior Art
Manipulators with a controlled gripper feed motion are used to achieve large and rapid feed motions of the workpiece in automatically integrated forging operations of a forging press and a forging manipulator. That is to say, grippers supporting the workpiece are rapidly advanced during the press return stroke when the workpiece is released, and are retained relative to the travel of the manipulator truck during the forging of press forming operation, or the gripper support is controlled so that a speed of equal magnitude but opposite to the speed of the manipulator truck is imparted to said gripper support which remains fixed in space relative to the ground. In this method of operation the manipulator truck traverses at a constant speed. The feed motion and relative operating motion of the gripper support is provided by hydraulic cylinders disposed between the gripper support and the manipulator truck.
Complicated free form forging operations require separate and manual operation of press and manipulator, and a horizontal gripper support resilience or cushioning in place of the controlled gripper support feed motion. Such axial resilience of the gripper support is provided by connection of the hydraulic cylinders to hydraulic accumulators.
The hydraulic cylinders are commonly double cylinders, disposed one behind the other and comprising a single cylinder casing which is divided in the middle of the longitudinal axis of the cylinder by means of a bulkhead (see U.S. Pat. No. 3,370,452). The pistons, usually double acting, have their principal piston surface or crown oriented towards the bulkhead or towards the cylinder base of the cylinder concerned. The annular surfaces of the piston adjoining the piston rods are outwardly oriented. The ends of the respective piston rods are pivotably mounted on the one hand on the manipulator truck and on the other hand on the gripper support. In the forward direction of movement of the manipulator truck the rear piston is hydraulically supported by the cylinder casing and in the reverse direction of movement of the manipulator truck it is the front piston which is thus supported.
Given suitable hydraulic control, this construction permits controlled gripper support feed motion, i.e. the return motion, into the starting position, of the gripper support relative to the manipulator truck after the forging operation of the forging stroke of the press, and also permits operation to provide horizontal gripper spring suspension when hydraulic fluid is displaced from the cylinder into the pressure accumulator which charges the said cylinder.
Howwever, the long structural length and the associated risk of buckling which arises with long stroke lengths, and the arrangement of the cylinder or cylinders in the forging manipulator itself, were found to be detrimental.
Some examples of mounting known hydraulic cylinders will be explained below:
1. Arrangement of the cylinder on the end of the gripper support results in the following disadvantages:
a. A large pivoting angle between the fixed rear suspension point on the manipulator truck and that of the gripper support owing to the required angle of inclination of the latter, also that caused by parallel motion of the gripper support and parallel displacement perpendicularly to its longitudinal axis, PA1 b. Power is transmitted over the entire gripper support casing, PA1 c. A large amount of space is required between the gripper support end and the cross-member of the manipulator truck frame. PA1 a. A large, although improved, pivoting angle, caused by the necessary inclination of the gripper support as well as during the parallel stroke, PA1 b. Power in this case is also transmitted via the entire support casing, PA1 c. Only insignificantly improved space requirements between the gripper support end and the cross-member of the manipulator truck frame. PA1 a. An advantageous small pivoting angle when the gripper support performs its parallel stroke, PA1 b. A short power transmission distance in the gripper support casing. PA1 a. A different position of the individual cylinders with respect to each other when the gripper support is laterally displaced parallel with its longitudinal axis. Problems also arise with the controlled feed motion of the gripper and gripper support. PA1 b. Lateral guidance of the gripper support by the frame of the manipulator truck is not possible. The quality of forging is therefore impaired. PA1 a. Advantageous pivoting angle during the parallel stoke of the gripper support. PA1 b. A short power transmission distance in the gripper support casing. PA1 c. Lateral guidance of the gripper support by the frame of the manipulator truck is ensured. PA1 a. An unfavorable bending moment along the front support axis of the gripper support. PA1 b. A broader manipulator frame and center distance between the rails is required. PA1 a. An advantageous pivoting angle when the gripper support performs its parallel stroke. PA1 b. A short power transmission distance in the support casing. PA1 c. Lateral guidance of the gripper support on the frame of the manipulator truck is ensured. PA1 d. Power transmission to the front support axis of the gripper support is advantageous. PA1 a. A longer gripper support is required to arrange the cylinder pairs between the front and rear support axis of the gripper support. PA1 b. A longer side is required for the frame of the manipulator truck to accomodate the gripper support.
2. The lateral arrangement of the cylinder pair on the rear gripper support suspension results in the following disadvantages:
3. Lateral arrangement of the cylinder pair, on the one hand on the front gripper support member and on the other hand on the side member or frame of the manipulator truck in an arrangement in which the piston-cylinder units are not parallel with the axis of the gripper support: